Bug 269980 ResourceLookup#selectFileForLocation(...) may now return non-existant IFiles (as the equivalent platform methods do).

- FileRelevance consider IFIle#isAccessible() & link state when computing IFile relevance
  - Tweak consumers who assume that ResourceLookup returns null for inaccessible IFiles

core/org.eclipse.cdt.core/parser/org/eclipse/cdt/core/index/IndexLocationFactory.java

@@ -110,7 +110,7 @@ public class IndexLocationFactory {
 	public static IIndexFileLocation getIFLExpensive(ICProject cproject, String absolutePath) {
 		final IProject preferredProject= cproject == null ? null : cproject.getProject();
 		IFile file= ResourceLookup.selectFileForLocation(new Path(absolutePath), preferredProject);
-		if (file != null)
+		if (file != null && file.exists())
 			return getWorkspaceIFL(file);
 
 		return getExternalIFL(absolutePath);

core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/rewrite/changegenerator/ChangeGenerator.java

@@ -231,7 +231,7 @@ public class ChangeGenerator extends CPPASTVisitor {
 			String currentFile = targetLocation.getFileName();
 			IPath implPath = new Path(currentFile);
 			IFile relevantFile= ResourceLookup.selectFileForLocation(implPath, null);
-			if (relevantFile == null) { // if not in workspace or local file system
+			if (relevantFile == null || !relevantFile.exists()) { // if not in workspace or local file system
 			    throw new UnhandledASTModificationException(modification);
 			}
 			MultiTextEdit edit;

core/org.eclipse.cdt.core/src/org/eclipse/cdt/core/ErrorParserManager.java

@@ -296,13 +296,16 @@ public class ErrorParserManager extends OutputStream {
 	 * Find exact match in the workspace. If path is not absolute search is done in working directory.
 	 * 
 	 * @param path - file path.
-	 * @return - file in the workspace or {@code null}.
+	 * @return - file in the workspace or {@code null} if such a file doesn't exist
 	 */
 	protected IFile findFileInWorkspace(IPath path) {
 		if (!path.isAbsolute()) {
 			path = getWorkingDirectory().append(path);
 		}
-		return ResourceLookup.selectFileForLocation(path, fProject);
+		IFile f = ResourceLookup.selectFileForLocation(path, fProject);
+		if (f != null && f.isAccessible())
+			return f;
+		return null;
 	}
 
 	/**

core/org.eclipse.cdt.core/src/org/eclipse/cdt/internal/core/resources/FileRelevance.java

@@ -16,6 +16,7 @@ import org.eclipse.cdt.core.model.ICProject;
 import org.eclipse.cdt.internal.core.model.CModelManager;
 import org.eclipse.core.resources.IFile;
 import org.eclipse.core.resources.IProject;
+import org.eclipse.core.resources.ResourceAttributes;
 
 /**
  * This class computes a relevance for files in case we have to select
@@ -26,27 +27,42 @@ public class FileRelevance {
 	private static final int CDT_PROJECT 			= 0x20;
 	private static final int ON_SOURCE_ROOT			= 0x10;
 
+	// Penalty for undesirable attributes
+	private static final int LINK_PENALTY			= 1;
+	private static final int INACCESSIBLE_SHIFT 	= 4;
+
 	/**
 	 * Compute a relevance for the given file. The higher the score the more relevant the
 	 * file. It is determined by the following criteria: <br>
 	 * - file belongs to preferred project <br>
 	 * - file belongs to a cdt-project <br>
 	 * - file belongs to a source folder of a cdt-project <br>
+	 * - file is accessible
+	 * - file is not a link
 	 * @param f the file to compute the relevance for
-	 * @return -1 if f1 is preferable, 1 if f2 is preferable, 0 if there is no difference.
+	 * @return integer representing file relevance. Larger numbers are more relevant
 	 */
 	public static int getRelevance(IFile f, IProject preferredProject) {
 		int result= 0;
 		IProject p= f.getProject();
-		if (p.equals(preferredProject)) 
+		if (p.equals(preferredProject))
 			result+= PREFERRED_PROJECT;
 
 		if (CoreModel.hasCNature(p)) {
 			result+= CDT_PROJECT;
 			ICProject cproject= CModelManager.getDefault().create(p);
-			if (cproject.isOnSourceRoot(f)) 
+			if (cproject.isOnSourceRoot(f))
 				result+= ON_SOURCE_ROOT;
 		}
+
+		if (!f.isAccessible())
+			result >>= INACCESSIBLE_SHIFT;
+		else {
+			ResourceAttributes ra = f.getResourceAttributes();
+			if (f.isLinked() || (ra != null && ra.isSymbolicLink()))
+				result -= LINK_PENALTY;
+		}
+
 		return result;
 	}
 }

core/org.eclipse.cdt.core/src/org/eclipse/cdt/internal/core/resources/ResourceLookup.java

@@ -72,6 +72,7 @@ public class ResourceLookup {
 	 * @param location an URI for the location of the files to search for.
 	 * @param preferredProject a project to be preferred over others, or <code>null</code>.
 	 * @return a file for the location in one of the given projects, or <code>null</code>.
+	 * 			NB the returned IFile may not exist
 	 */
 	public static IFile selectFileForLocationURI(URI location, IProject preferredProject) {
 		return selectFile(findFilesForLocationURI(location), preferredProject);
@@ -84,6 +85,7 @@ public class ResourceLookup {
 	 * @param location a path for the location of the files to search for.
 	 * @param preferredProject a project to be preferred over others, or <code>null</code>.
 	 * @return a file for the location or <code>null</code>.
+	 * 			NB the returned IFile may not exist
 	 */
 	public static IFile selectFileForLocation(IPath location, IProject preferredProject) {
 		return selectFile(findFilesForLocation(location), preferredProject);
@@ -92,26 +94,21 @@ public class ResourceLookup {
 	private static IFile selectFile(IFile[] files, IProject preferredProject) {
 		if (files.length == 0)
 			return null;
-		
-		if (files.length == 1) {
-			final IFile file= files[0];
-			if (file.isAccessible())
-				return file;
-		}
-		
+
+		if (files.length == 1)
+			return files[0];
+
 		IFile best= null;
 		int bestRelevance= -1;
-		
+
 		for (int i = 0; i < files.length; i++) {
 			IFile file = files[i];
-			if (file.isAccessible()) {
-				int relevance= FileRelevance.getRelevance(file, preferredProject);
-				if (best == null || relevance > bestRelevance ||
-						(relevance == bestRelevance && 
-								best.getFullPath().toString().compareTo(file.getFullPath().toString()) > 0)) {
-					bestRelevance= relevance;
-					best= file;
-				}
+			int relevance= FileRelevance.getRelevance(file, preferredProject);
+			if (best == null || relevance > bestRelevance ||
+					(relevance == bestRelevance && 
+							best.getFullPath().toString().compareTo(file.getFullPath().toString()) > 0)) {
+				bestRelevance= relevance;
+				best= file;
 			}
 		}
 		return best;
@@ -128,11 +125,6 @@ public class ResourceLookup {
 	public static void sortFilesByRelevance(IFile[] filesToSort, final IProject preferredProject) {
 		Collections.sort(Arrays.asList(filesToSort), new Comparator<IFile>() {
 			public int compare(IFile f1, IFile f2) {
-				boolean a1= f1.isAccessible();
-				boolean a2= f2.isAccessible();
-				if (a1 != a2) 
-					return a1 ? -1 : 1;
-		
 				int r1= FileRelevance.getRelevance(f1, preferredProject);
 				int r2= FileRelevance.getRelevance(f2, preferredProject);